Brachymetatarsia is a condition in which one of the five long bones of the foot (the metatarsals) is abnormally short, resulting in a shortened toe. This condition usually occurs in both feet (i.e., bilaterally) and in the fourth toe. If it affects more than one toe, the condition is called brachymetapody.
Causes of Brachymetatarsia
In most cases, brachymetatarsia results when the metatarsal growth plate closes too early. Once the growth plate closes, the bone can no longer grow. This can be caused by a genetic factor or by trauma to the foot that results in a metatarsal growth plate fracture.
Physiology of Brachymetatarsia
A shortened toe can cause several problems. During walking, the weight normally is transferred from the fifth toe to the fourth, then to the third, and so on until it reaches the first toe (hallux). This occurs because the toes are gradually longer and as weight is transferred to the forefoot, the next longest toe assumes the weight. Brachymetatarsia disrupts this process.
If the fourth toe is shorter than the fifth toe, it never assumes the body weight and cannot transfer it to the third toe correctly. As a result, the fifth and third toes receive extra weight and pain develops in those areas. An abnormally short toe also tends to drift upward, which often causes problems with footwear.